A Romanian airfield. The country is suspected of having a secret detention centre. Photograph: Bogdan Cristel/Reuters

The full extent of European collusion with the CIA during operations to abduct terrorism suspects and fly them to countries where they may be tortured is laid bare today by the continent's most authoritative human rights body.

Several states have allowed the agency to snatch their own residents, others have offered extensive logistical support, while many have turned a blind eye, according to the Council of Europe.

The UK stands accused of not only allowing the use of British airspace and airports, but of providing information that was used during the torture of one suspect. The report adds that there is strong evidence to suspect two European states, Poland and Romania, of permitting the CIA to operate secret prisons on their soil, despite official denials.

'Active participation'

The report follows an investigation by Dick Marty, chairman of the Council's legal affairs and human rights committee. It has been obtained by the Guardian ahead of its publication in Paris today. Mr Marty says that far from being hoodwinked by a "CIA plot", 14 European states were fully aware of much of what was going on. "It is now clear - although we are still far from having established the whole truth - that authorities in several European countries actively participated with the CIA in these unlawful activities. Other countries ignored them knowingly, or did not want to know."

Although Mr Marty concludes that the US must bear responsibility for the extraordinary rendition, he says the programme could operate only with "the intentional or grossly negligent collusion of the European partners".

The inquiry was launched in November amid political outrage over reports, first published in the Washington Post, of the existence of CIA detention centres in Eastern Europe. Other media investigations, including one by the Guardian, had uncovered evidence of the use of British and other European airports by aircraft that have been involved in renditions.

A breakthrough in Mr Marty's inquiry came with agreement by EuroControl, the air traffic agency, to hand over thousands of records of flight plans filed electronically with controllers by the pilots of alleged CIA planes since 2001. While the majority of the flights had nothing to do with prisoner operations, Mr Marty's report provides the first official confirmation that some flights correspond with the accounts given by prisoners of their abduction and transfer to secret jails by the CIA.

His report highlights the movement of 18 suspects, all of which used European facilities or airspace, which are part of a series of "rendition circuits" which he likens to a "spider's web spun across the globe". He warns that the US, believing that "neither conventional judicial instruments nor those established under the framework of the laws of war could effectively counter the new forms of international terrorism" has decided to "develop new legal concepts" that have left hundreds of terrorist suspects deprived of their liberty, outside US territory but under US control and denied any access to their fundamental legal rights. "This legal approach is utterly alien to the European tradition and sensibility, and is clearly contrary to the European Convention on Human Rights and the Universal Declaration of Human Rights."

Mr Marty says that while Spain, Turkey, Germany and Cyprus have provided staging posts for rendition operations, Italy, Sweden, Bosnia, and Macedonia have all allowed the rendition of their residents from their soil. He accuses the latter of covering up its involvement in the CIA rendition of a German citizen, Khaled el-Masri, to Afghanistan, after he arrived in Macedonia in January 2004. Britain - like Ireland, Portugal, and Greece - is described as providing stopovers for CIA planes, but the greatest criticisms levelled against London are about the handing over of information about its residents and former residents that has, says Mr Marty, led to renditions and torture. For instance, information about a former London student, Benyam Mohammed, 27, is alleged to have been used during his torture in Morocco, where he was taken following his arrest in Pakistan.

Finally, Mr Marty alleges there is enough concrete evidence, mainly consisting of flight data, to support suspicions that Romania and Poland have allowed the operation of secret CIA detention centres on their soil, despite official denials.

Detention centres

The evidence against Romania, he says, comes from a "rendition circuit" involving a CIA Boeing 737 with registration N313P, that began in Cyprus on January 21 2004. The plane and the CIA team on board went from Cyprus to Morocco the following day to pick up Benyam Mohammed and take him to Afghanistan. The plane then returned to Europe to render el-Masri, on January 24, also to Afghanistan. Finally, Mr Marty believes, the pattern of the flight indicates it transferred another suspect from Afghanistan to a secret detention place in Romania.

The drop-off in Romania could not be explained, says Mr Marty, by any need to refuel. "The most likely hypothesis is that the purpose of this flight was to transport one or several detainees from Kabul to Romania," he concludes. He adds that although he has not uncovered definitive evidence of a secret detention centre in Romania, his findings justify further investigation. Romania, he adds, "is thus far the only Council of Europe member state to be located on one of the rendition circuits we believe we have identified, and which bears all the characteristics of a detainee transfer or drop-off point".

Mr Marty also highlights a number of flights from Afghanistan to Poland at times when it is now known that terrorism suspects were being transferred from Kabul to unknown destinations. His suspicions were fuelled by the Polish authorities' failure to cooperate: while EuroControl's records detailed a series of flights into the country, including a number to the Szymany air base, north east of Warsaw, local officials claimed they had no records of the visits. Mr Marty describes that as "highly unusual", and adds: "Poland cannot be considered to be outside the rendition circuits simply because it has failed to furnish information corroborating my data from other sources."